You remind me of something that I didn't think about earlier -- that 3072x2304 resolution could only be internal, and they may ship a 9.7 inch iPad with a lower resolution panel.
Regarding the 12 inch iPad, I think Apple will use a new resolution for this entirely. As they've already shown, they understand that a bigger device needs to display more content, not bigger content.
Yeah, hence the 2560x1920 prediction for the 12.1" MaxiPad.
As for the 9.7", I don't think it really makes much sense to take a Retina 9.7" iPad and then update it to make it render internally at 3X 3072x2304, only to downsample it again, when the original 2048x1536 is already decent Retina at 264 ppi.
However, for a 12.1" iPad, downsampling from 3X makes sense, since increasing the final resolution to 2560x1920 brings it to the exact same 264 ppi as the 9.7" iPad. That also simplifies management of their supply sourcing since it's the same panel tech as the 9.7" iPad.
I seem to recall seeing a rumour that the MaxiPad would be a hybrid device running OS X. Which to me makes sense, because it would be competing with the Surface Pro in size and price point.
Apple still lacks a touch screen enabled laptop. Which is something Microsoft has really been stressing in their ads for the Surface Pro 3. I actually really do like concept of the Pro. Apple's already got the tech in the form of the MBA. I'd buy something like that.
Though I consider something like that to be fairly unlikely. I don't think Apple wants to start fragmenting the iDevice line by using different hardware architecture. Secondly, I don't think they want to marginalize the MBA either. Be interesting to see what they come up with. What I don't want is a slightly faster, slightly bigger, more expensive iPad Air. 10'' is the perfect screen size for those devices. Any bigger and I want something that works as a full computer.
10" only makes sense in certain circumstances... like the MS Surface 2 line. That unit is a 1080p 1.78:1 unit, which means it's quite wide for its 10.6" screen size. The unit width is 275 mm, which is 10.8" wide.
Why does that 10.8" width matter? Because that's close to the smallest size a machine can be and still have a full-sized keyboard.
You'll note that the 4:3 12" iBook, the 4:3 12" PowerBook, and the 1.6:1 11.6" MacBook Air, all have full-sized keyboards.
For the Microsoft Surface Pro 3, they decided to change from a 1.78:1 unit to a 1.5:1 12" size. That unit is 11.5" wide, and also has a full-sized keyboard. Just as importantly, it increases the vertical height to give more room in laptop landscape mode, and it also provides more room for a decent sized trackpad.
In contrast, the 4:3 9.7" iPad is only 9.4" wide, which is insufficient width for a full-sized keyboard. That's why all the 3rd party keyboards have reduced-size keys, and no decent trackpads.